Using Joint Dimension for your 1:1 relation is the right design. 2016-12-02 0:21 GMT+08:00 Alberto Ramón <[email protected]>:
> Nice Liu > > We have some cases like > DayWeekTXT , DayWeekID > MonthTXT, MonthID > > small proposal: > Can would be interesting create Derived with 1:1 relation, with support > for filters and Group by > > 2016-12-01 11:55 GMT+01:00 Billy(Yiming) Liu <[email protected]>: > >> The cost of joint dimension compared with extended column is you have >> more columns in the HBase rowkey. It may harm the query performance. But >> most time, joint dimension is still recommended, since the normal dimension >> column supports much more functions than extended column, such as count(*). >> >> 2016-12-01 17:07 GMT+08:00 Alberto Ramón <[email protected]>: >> >>> Hello >>> I was preparing a email with related doubts: >>> >>> Some times we have derived dimensions with relation 1:1, examples: >>> WeekDayID & WeekDayTxt >>> MonthID & WeekTxt >>> >>> SOL1: Derived. ID as Host and Txt Extended >>> PB: You can't filter / Group by Txt >>> >>> SOL2: Joint. Define tuples of ID & TXT >>> Some PB/limitation? (I need test this option) >>> >>> 2016-12-01 0:35 GMT+01:00 Billy(Yiming) Liu <[email protected]>: >>> >>>> Thanks, Alberto. The explanation is accurate. EXTENDED_COLUMN is only >>>> used for representation, but not filtering or grouping which is done by >>>> HOST_COLUMN. So EXTENDED_COLUMN is not a dimension, it works like a >>>> key/value map against the HOST_COLUMN. >>>> >>>> If the value in EXTENDED_COLUMN is not long, you could just define two >>>> dimensions with joint dimension setting, it has almost the same performance >>>> impact with EXTENDED_COLUMN which reduces one dimension, but better >>>> understanding. >>>> >>>> 2016-11-30 19:00 GMT+08:00 Alberto Ramón <[email protected]>: >>>> >>>>> This will help you >>>>> http://kylin.apache.org/docs/howto/howto_optimize_cubes.html >>>>> >>>>> The idea is always, How I can reduce the number of Dimension ? >>>>> If you reduce Dim, the time / resources to build the cube and final >>>>> size of >>>>> it decrease --> Its good >>>>> >>>>> An example can be DIM_Persons: Id_Person , Name, Surname, Address, >>>>> ..... >>>>> Id_Person can be HostColumn >>>>> and other columns can be calculated from ID --> are Extended Column >>>>> >>>>> >>>>> >>>>> >>>>> 2016-11-30 11:35 GMT+01:00 仇同心 <[email protected]>: >>>>> >>>>> > Hi ,all >>>>> > I don’t understand the usage scenarios of EXTENDED_COLUMN,although >>>>> I saw >>>>> > this article “https://issues.apache.org/jira/browse/KYLIN-1313”. >>>>> > What,s the means about parameters of “Host Column” and “Extended >>>>> Column”? >>>>> > Why use this expression,and what aspects of optimization that this >>>>> > expression solved? >>>>> > Can be combined with a SQL statement to explain? >>>>> > >>>>> > >>>>> > Thanks~ >>>>> > >>>>> >>>> >>>> >>>> >>>> -- >>>> With Warm regards >>>> >>>> Yiming Liu (刘一鸣) >>>> >>> >>> >> >> >> -- >> With Warm regards >> >> Yiming Liu (刘一鸣) >> > > -- With Warm regards Yiming Liu (刘一鸣)
